Tamper indicator

Abstract

A tamper-detection switch is built into a device such as an encoder for a gas or water meter. The switch has a contact arm biased to complete an alarm circuit, but this is prevented by a restraining post. On installation, an actuator is moved by contact with the meter to lift the contact arm free of the restraining post, at the same time restraining the arm from completing the circuit. If the encoder is subsequently moved away from the meter, a biasing spring causes the actuator to move out of the path of the contact arm, freeing it to complete the alarm circuit. BACKGROUND OF THE INVENTION

What I claim is: 
     
       1. An indicator system for signaling the movement of a first device away from a second device comprising, a support fixed in the first device, an elongated contact element associated at one end with a first terminal mounted on the support, a second terminal mounted on the support, said terminals being adapted for connection to an alarm signal circuit, means biasing the contact element toward the second terminal, first restraining means fixed on the support in a position to hold the contact element out of contact with the second terminal, an actuating element movable into and out of the path of movement of the contact element between its restrained position and its contacting position and into engagement with the contact element in its restrained position, means biasing said actuating element out of said path, and means fixed on the second device in a position to move the actuating element against the contact element to dislodge it from the restraining means when the first device is attached to the second device, the actuating element being adapted to act as a second restraining means, whereby separation of the first device from the second device permits the actuating element to move out of the path of movement of the contact element which then contacts the second terminal. 
     
     
       2. An indicator system according to claim 1 wherein the contact element, when contacting the second terminal, is out of the path of movement of the actuating element. 
     
     
       3. An indicator system according to claim 1 wherein the support is flat and the actuating element is a rod movable perpendicularly to the surface of the support. 
     
     
       4. An indicator system according to claim 3 wherein the actuating element is provided with a flat surface adapted to engage the contact element for dislodging it and with a post adapted to act as a second restraining means. 
     
     
       5. An indicator system according to claim 1 wherein the contact element is a spring wire. 
     
     
       6. An indicator system according to claim 1 wherein the contact element includes a coil spring portion and two straight positions. 
     
     
       7. An indicator system according to claim 6 wherein the coil spring portion is coiled around a support, one straight portion projects therefrom a distance sufficient to engage the first restraining means and the second terminal, and the other straight portion is connected to the first terminal. 
     
     
       8. An indicator system according to claim 1 wherein the means fixed on the second device is a plate adapted to engage an end of the actuating element. 
     
     
       9. An indicator system according to claim 1 wherein the means fixed on the second device is a pin adapted to engage an end of the actuating element. 
     
     
       10. An indicator system according to claim 1 wherein the first device is an encoder adapted for attachment to a meter and the second device is an energy monitoring meter.